Plastic materials of many kinds are suitable for recycling to provide raw material for the manufacture of other plastic articles. The wide variety and increasing popularity of plastic containers for various consumer foodstuffs and other products is a bountiful source of plastic suitable for recycling. These products include milk jugs, plastic soft-drink bottles, and tubs or bottles used for packaging condiments and other products. These plastic articles typically are discarded after a single use and are known as post-consumer scrap plastic.
This plastic scrap is segregated from other waste by processors of collected waste and is baled to compress the scrap containers into a relatively dense package suitable for shipment to a recycling facility. This baled consumer scrap usually includes a variety of different kinds of plastic materials, determined by the requirements of appearance and structural strength for the particular containers. For example, plastic milk jugs are made of material having substantial structural strength so that the jugs are not easily ruptured in use and maintain their desired shape when filled with a gallon of liquid. For these reasons, milk jugs are made of high-density polyethylene (HDPE) in a natural state having an opaque white color. Other beverages such as soft drinks are sold in quart or liter plastic bottles which require less structural strength to maintain their shape and to provide stackability, and usually are in bottles of less-costly plastic material such as polyethylene terephthalate (PET). These PET plastic containers may be clear to permit consumer viewing of the contents, or may be colored to protect the contents from exposure to light or for cosmetic appearance. These latter plastic products are known as colored HDPE. Still other food stuffs such as butter, condiments, and the like usually are sold to consumers tubs or other packages of HDPE with a color additive to meet the cosmetic or marketing needs of the merchandiser.
These four kinds of plastics, namely, colored HDPE, green PET, clear PET, and natural HDPE, define the four categories into which most post-consumer scrap plastic fall. Effective recycling of post-consumer plastic requires separating the baled plastic scrap into those four constituents or fractions for most effective recycling, because the color and the organic properties of the fractions determine the best uses of the recycled scrap. Furthermore, some of the containers making up these scrap fractions, especially the containers made of colored HDPE or natural HDPE, have external labels of paper or foam plastic which are considered foreign matter contaminating the scrap for recycling. Removal of this foreign matter from the underlying plastic container thus is required for effective recycling. The containers made of PET usually have the label information printed directly on the container instead of applied as a separate entity onto the container and thus usually do not present the same contaminating problem as HDPE scrap bearing a separate label made of a foreign substance.